New Device Lets Plants Talk

Smart sensors let crops text-message growers for more water

4 May 2009—Although technology has benefited agriculture in a number of ways, there are some things that growers still do the old-fashioned way. Among them is putting their hands and other measuring devices in the dirt and judging, based on how moist the soil is, whether their crops need water and how much should be added.

But AgriHouse, an agricultural technology firm based in Berthoud, Colo., says it is marketing a new device that can eliminate irrigation guesswork by letting plants call growers via cellular networks to indicate when they need a drink. To be specific, the plants send text messages alerting growers if their water uptake is too little, too much, or just right.

AgriHouse’s leaf sensor clips onto a plant’s leaf and uses proprietary algorithms to translate its relative level of turgidity into a reading of its internal moisture content. Developed by the University of Colorado at Boulder for NASA’s human space missions and licensed exclusively by AgriHouse, the new sensors are set to be sold in early 2010.

The AgriHouse field station, a small, weatherproof electrical enclosure to which several of the centimeter-long turgidity sensors are wired, collects readings every few minutes, then sends packets of data over the cellular network to a secure, password-protected Web portal every few hours. The system can be programmed to activate an irrigation system or send an alert whenever the plant’s water-deficit stress levels fall outside a preset range.

Though too little or too much water can diminish yields, growers tend to err on the side of giving crops more water than they need rather than risk letting the crops dry up and wilt. AgriHouse claims their sensors could significantly lower the world’s freshwater usage by preventing plants from getting too much water at the wrong time. Commercial agriculture in the United States accounts for more than 60 percent of the freshwater consumed annually. This equates to roughly 129 billion liters per day, according to the U.S. Geological Survey. ”A savings of just 10 percent would be dramatic,” says Richard Stoner, founder and president of AgriHouse. Asked how big a savings the leaf sensor would likely yield, he notes that the amount varies by species of plant but that an annual reduction of 5 to 10 centimeters per hectare in applied water use would be feasible for most irrigated row crops.

Stoner says that for each circular 53-hectare field irrigated by a center pivot (a large rotating sprinkler system), the water savings realized by growers who clip a few of the sensors to their plants ”would be enough to supply as many as 50 U.S. homes annually.” Stoner notes that there are close to 200 000 center pivots in North America, ”so that’s a lot of freshwater that can be diverted to other uses.” He adds that for each of these center pivots, two to four sensors will provide enough redundancy to make an accurate assessment of what is transpiring in the fields.

On the flip side of the water-conservation coin is reduced energy use. You wouldn’t imagine that farming, which brings to mind pictures of idyllic meadows and rustic barns, is an energy-intensive business. But the energy required for water delivery—to pump water from wells, lakes, or reservoirs and distribute it across fields dotted with thirsty plants—accounts for half of a grower’s input costs, says Stoner. Under a typical center-pivot irrigation system, he adds, the water conserved by using AgriHouse’s leaf sensors could save a grower as much as US $4000 in annual pumping costs while substantially reducing carbon emissions. As for the sensors, they draw a miserly 50 milliwatts from the field station, which contains a lithium-ion battery pack that can store enough energy to run from the time seeds are sown in spring to when the crops are harvested in the fall.